A reason to follow service intervals for RMZ & KXF 250 owners

Discussion in 'Technical Posts' started by Rich Rohrich, Oct 17, 2004.

  1. Rich Rohrich

    Rich Rohrich BioHazard

    Joined:
    Jul 27, 1999
    Messages:
    22,149
    Media:
    6
    Featured Threads:
    5
    Likes Received:
    10,908
    Trophy Points:
    1,325
    The new breed of four-strokes have much shorter service intervals than the old XR style bikes we are used to. Despite the service interval recommendations in the manual a lot of folks who are racing these bikes are choosing to ignore them.



    Under the heading a picture is worth a thousand words here's a graphic example of what tends to happen when you run the stock valve components too long. These pics are from a KXF 250 that I worked on yesterday.

    If the springs and valves would have been changed more in line with the service intervals this wouldn't have happened. As a result the head is destroyed beyond repair, the barrel is junk, and the rod was bent and a bunch of other pieces are now scrap. Take specific note of the exploded tappet/bucket in the cam side view. Luckily the rider didn't get hurt when it let go. The interesting part is, with all this carnage the cam journal without an oil groove that people are worried about is in perfect condition.

    The moral of the story is, if you are racing a 250F invest in an hour meter and pay attention to the service intervals.

    Click the links below for the full size hi-res versions of the pictures

    KXF Head & Piston
    KXF Head close up
    KXF Head broken bucket
    KXF broken valve
  2. Rich Rohrich

    Rich Rohrich BioHazard

    Joined:
    Jul 27, 1999
    Messages:
    22,149
    Media:
    6
    Featured Threads:
    5
    Likes Received:
    10,908
    Trophy Points:
    1,325
    While we are on the subject of reliability there is something that I have been meaning to address on these engines for a while but up until now it has been fairly speculative on my part so I have been reluctant to say anything. The main bearings in the KXF/RMZ engine are pressed into the cases with a very light interference fit, but unlike most designs of this type there is no locking plate in the case to keep the bearing secure. Keep in mind this engine has no counter balancer so there tends to be a bit more crank mass than say a YZF250 and as a result it looks like it subjects the main bearings to a different type of load than a counter balancer equipped engine.

    The point is, more and more it looks like as these engines get a lot of hours on them the main bearing saddle in the case looks to be loosening up and allowing the main bearings to move around. This looks to be especially prevelant on the ignition side. Red loctite usage and carefull installation of new bearings looks like a temporary fix, but long term these engines when raced will probably wear the cases to the point of needing complete replacement.

    Eric and I are looking at the possibility of using a bearing and lock plate setup similar to what Yamaha and Honda are using in the hopes of keeping folks from having to treat case replacement as part of their annual maintenance. As we work more on this I'll pass along any info I can. In the mean time pay particular attention to the main bearings when you are doing your crank maintenance.
  3. VintageDirt

    VintageDirt Baked Spud

    Joined:
    Jan 1, 2001
    Messages:
    3,077
    Likes Received:
    0
    Trophy Points:
    36
    I tell ya, some people...:)

    But seriously, Rich I bought an hour meter and I can't for the life of me find maintenance intervals in hours. Is it my 3rd grade reddin compenshin or somethin else. Maybe you could list the important intervals in hours. :worship:
  4. Chili

    Chili Lifetime Sponsor - Photog Moderator

    Joined:
    Apr 9, 2002
    Messages:
    8,502
    Likes Received:
    2
    Trophy Points:
    38
    Ok time for the hot seat Rich. We are probably giving in to the lure of the darkside for LazyBoy for next season. He really isn't fond of the handling of the Yamaha's so we had kind of ruled out the YZF. Honda really doesn't have a dealer locally that supports our MX scene so I had always preferred to spend my money going yellow or green and supporting what I felt were superior dealers for my needs. Based on the bearing issue do you feel there will still be more reliability/design issues with the KXF/RMz even if you are anal about your maintenance intervals? Based on the Green/Yellow issues this year I had pretty much decided to go red for 05 but everytime I go out to the Zook dealer I leave wondering/hoping the bike is better for 05 and worth a risk so I can support the dealer.
  5. JUSTRIDE415

    JUSTRIDE415 Subscriber

    Joined:
    Oct 26, 2001
    Messages:
    190
    Likes Received:
    0
    Trophy Points:
    0
    I printed these pictures to give them to my suzuki riding buddies!
  6. Rich Rohrich

    Rich Rohrich BioHazard

    Joined:
    Jul 27, 1999
    Messages:
    22,149
    Media:
    6
    Featured Threads:
    5
    Likes Received:
    10,908
    Trophy Points:
    1,325
    Doug - I've owned a whole bunch of Suzukis over the years and loved each one, but at the risk of annoying people and being branded a Suzuki hater I'll tell you what we have told our other customers. Based on the way things stand today I would strongly advise AGAINST this bike if it is going to be raced/ridden hard on a consistent basis. There are far too many design and quality control issues to recommend it. It seems to be a nice bike for trail riders and slow pokes, but racing one will prove to be very expensive.

    Now, down the road we'll have a systems solution to the valve issues from Kibblewhite (springs, valves and tappets) so the valve issues should go away. Suzuki is claiming to have fixed the transmission and cooling system problems for 05, so that's a plus.

    If you decide have Troy race one I would suggest buying a spare head and setting it up with the Kibblewhite parts so it can be swapped out at the first piston change (15-20 hours) . You can easily sell off the spare OEM kitted head. Past that if you get used to the rather intense service requirements and roll the bikes over every year you aren't likely to run into any of the long term issues and will have a pretty nice bike. What new issues will crop up with the 2005s remains to be seen. I was really disappointed with how this bike turned out. I really had high hopes for it.

    Unfortunately seriously racing any of the new 250Fs can be seriously expensive but this one pushes it a little too hard.

    Maybe ochster will see this and share some of his experience with the bike. He was wrenching for a national level rider and has some really good insights on the issues that come with racing the RMZ.

    Wes - I'll try and put together a list of stuff for the various bikes. Good idea. :cool:
  7. Chili

    Chili Lifetime Sponsor - Photog Moderator

    Joined:
    Apr 9, 2002
    Messages:
    8,502
    Likes Received:
    2
    Trophy Points:
    38
    Thanks for the reply Rich. That's pretty much where we were at but I keep trying to find excuses to support this dealer.

    As for ochster did he switch riders? because I thought Ryan raced a CRF this summer instead of the zook.
  8. Rich Rohrich

    Rich Rohrich BioHazard

    Joined:
    Jul 27, 1999
    Messages:
    22,149
    Media:
    6
    Featured Threads:
    5
    Likes Received:
    10,908
    Trophy Points:
    1,325
    I haven't had a chance to talk to him lately. Maybe they switched brands for the reasons we just discussed.

    I'll send him a PM and ask him to jump in on this thread.
  9. ochster

    ochster Lifetime Sponsor

    Joined:
    Mar 11, 2000
    Messages:
    709
    Likes Received:
    0
    Trophy Points:
    0
    Rich has summed up the yellow/green versus other colors dilemia very well. Putting that aside the RMZ is a great handling and very competitive bike.

    Oversize radiators on the 04's are a must with fast riders and hot climates using a 1.6 or 1.8 cap. The oem radiator shrouds limit flow out the back of the radiator. A couple of stragtegically placed holes/slots helps. As does spacing the radiators out from the frame 1/2"-3/4". We use aluminum spacers and longer bolts with a longer connecting hose on the top. At a minimum do the spacing and holes/slots with a Boyesen water impeller kit and 1.6 cap, it works. We have had good luck with Race Kool from Precision Automotive, or 80-90% water and 10-20% antifreeze. Water pump seals are short lived, keep a spare or two. Headgaskets are notorious for leaks even when new. All the fasteners on the engine cases will loosen up regularly. The fastener quality is very poor, do not over torque. This is why many have leaking center cases and right side covers. Safety wire the drain bolt, its already drilled. The flywheels have been known to seperate. Do a visual check by pulling the left side cover occasionally, you will see damage to the magneto if the center is coming loose. They do use oil when rode hard, 2-3oz. in 30 minutes is common under race conditions with a higher compression piston. A hinson clutch cover will give you added capacity and delete the cover window wich some have broke. The rear shock linkage will bend bolts under hard moto. If your going have the frame powder coated, weld up all the gussets (especially at the stem head) and reinforce the steering stop. It's tiny and when it shears it takes out the frame and fork leg. The airbox is held to the subframe with two bolts up top by the seat, locktight them. The plastic tabs on the airbox break frequently. The intake boot on the carb is loose on most all bikes when new. The band clamp (at the head) stretches and bottoms before tightening in short order. Some have lost carbs, we safety wire the carb forward to the head and use a quality clamp. The hot start cable plunger in the carb is brass. Moisture will get in thier and corrode it solid to carb body in very short order. Undo the silly plastic nut and pull it out, apply some lube (I use silicone grease), do it frequently. Be very careful rethreading the plastic nut. If you do cross thread it or ruin the brass plunger, there is a kit for this that includes everything on the end of the cable for $20. Many overtighten the valve cover bolts and pull the threads out of the cam towers. Thier is a fair amount of CDI problems, not a bad idea to carry a spare.

    Rich and Kibblewhite is on top of the valve situation. It will be nice when the kits are ready next month. Bronze seats and frequent tappet and oem valve replacements for precaution have been working very well. Kibblewhite did just set me up with thier new bucket design, very nice. We have never had any cam journal issues.

    There have been shifting issues. Mostly related to shift pawl plate wearing a groove into the pawls, and worn/ bent forks and shafts. But still some are just notchy compared to others. Rich is right about the lifespan of centercases.

    Ryan Abrigo picked up a private Honda ride, he may be with Motosport outlet for 05'. I have been wrenching for Cole Siebler since the outdoors. We were actually trying to secure some help for a privateer supercross team, but it's tuff to round up $60,000-$85,000.
  10. Chili

    Chili Lifetime Sponsor - Photog Moderator

    Joined:
    Apr 9, 2002
    Messages:
    8,502
    Likes Received:
    2
    Trophy Points:
    38
    Thanks for the info Mark, I think we'll just go red or blue until they sort things out with the RMz. Good Luck with Cole, he looks like a heck of a rider. Seems his injuries probably cost him his spot on the Samsung team last year as I think he was one of the most talented riders they had.
  11. Rich Rohrich

    Rich Rohrich BioHazard

    Joined:
    Jul 27, 1999
    Messages:
    22,149
    Media:
    6
    Featured Threads:
    5
    Likes Received:
    10,908
    Trophy Points:
    1,325
    Ochster - Thanks for the VERY complete rundown of the RMZ issues you've had to deal with. This one will be going into the archives for sure. :worship:

    Best of luck to you and Cole in the coming season. As always if there is anything we can do to help you guys just holler. :cool:
  12. bclapham

    bclapham Lifetime Sponsor

    Joined:
    Nov 5, 2001
    Messages:
    4,558
    Likes Received:
    0
    Trophy Points:
    0
    wow!!! :yikes: :yikes:

    just out of interest Rich, how many hours did this bike have on it, and what class was the rider?

    Did anyone notice, all the KXF and RMZs got through the SX alright, but as soon as everyone showed up to the Glen Helen prequel to the nationals in May, these bikes started dropping like flies- guess they dont like to be revved!!!!!

    how much cash will it cost to make this bike work again Rich?



Share This Page